package cn.edu.pku.tools;

public class Base64Coder {  
	 
	//The line separator string of the operating system.  
	private static final String systemLineSeparator = System.getProperty("line.separator");  
	 
	//Mapping table from 6-bit nibbles to Base64 characters.  
	private static char[]    map1 = new char[64];  
	static {  
	   int i=0;  
	   for (char c='A'; c<='Z'; c++) map1[i++] = c;  
	   for (char c='a'; c<='z'; c++) map1[i++] = c;  
	   for (char c='0'; c<='9'; c++) map1[i++] = c;  
	   map1[i++] = '+'; map1[i++] = '/'; }  
	 
	//Mapping table from Base64 characters to 6-bit nibbles.  
	private static byte[]    map2 = new byte[128];  
	static {  
	   for (int i=0; i<map2.length; i++) map2[i] = -1;  
	   for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; }  
	 
	/**  
	* Encodes a string into Base64 format.  
	* No blanks or line breaks are inserted.  
	* @param s  A String to be encoded.  
	* @return   A String containing the Base64 encoded data.  
	*/ 
	public static String encodeString (String s) {  
	return new String(encode(s.getBytes())); }  
	 
	/**  
	* Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters.  
	* This method is compatible with <code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.  
	* @param in  An array containing the data bytes to be encoded.  
	* @return    A String containing the Base64 encoded data, broken into lines.  
	*/ 
	public static String encodeLines (byte[] in) {  
	return encodeLines(in, 0, in.length, 76, systemLineSeparator); }  
	 
	/**  
	* Encodes a byte array into Base 64 format and breaks the output into lines.  
	* @param in            An array containing the data bytes to be encoded.  
	* @param iOff          Offset of the first byte in <code>in</code> to be processed.  
	* @param iLen          Number of bytes to be processed in <code>in</code>, starting at <code>iOff</code>.  
	* @param lineLen       Line length for the output data. Should be a multiple of 4.  
	* @param lineSeparator The line separator to be used to separate the output lines.  
	* @return              A String containing the Base64 encoded data, broken into lines.  
	*/ 
	public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) {  
	int blockLen = (lineLen*3) / 4;  
	if (blockLen <= 0) throw new IllegalArgumentException();  
	int lines = (iLen+blockLen-1) / blockLen;  
	int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length();  
	StringBuilder buf = new StringBuilder(bufLen);  
	int ip = 0;  
	while (ip < iLen) {  
	   int l = Math.min(iLen-ip, blockLen);  
	   buf.append (encode(in, iOff+ip, l));  
	   buf.append (lineSeparator);  
	   ip += l; }  
	return buf.toString(); }  
	 
	/**  
	* Encodes a byte array into Base64 format.  
	* No blanks or line breaks are inserted in the output.  
	* @param in  An array containing the data bytes to be encoded.  
	* @return    A character array containing the Base64 encoded data.  
	*/ 
	public static char[] encode (byte[] in) {  
	return encode(in, 0, in.length); }  
	 
	/**  
	* Encodes a byte array into Base64 format.  
	* No blanks or line breaks are inserted in the output.  
	* @param in    An array containing the data bytes to be encoded.  
	* @param iLen  Number of bytes to process in <code>in</code>.  
	* @return      A character array containing the Base64 encoded data.  
	*/ 
	public static char[] encode (byte[] in, int iLen) {  
	return encode(in, 0, iLen); }  
	 
	/**  
	* Encodes a byte array into Base64 format.  
	* No blanks or line breaks are inserted in the output.  
	* @param in    An array containing the data bytes to be encoded.  
	* @param iOff  Offset of the first byte in <code>in</code> to be processed.  
	* @param iLen  Number of bytes to process in <code>in</code>, starting at <code>iOff</code>.  
	* @return      A character array containing the Base64 encoded data.  
	*/ 
	public static char[] encode (byte[] in, int iOff, int iLen) {  
	int oDataLen = (iLen*4+2)/3;       // output length without padding  
	int oLen = ((iLen+2)/3)*4;         // output length including padding  
	char[] out = new char[oLen];  
	int ip = iOff;  
	int iEnd = iOff + iLen;  
	int op = 0;  
	while (ip < iEnd) {  
	   int i0 = in[ip++] & 0xff;  
	   int i1 = ip < iEnd ? in[ip++] & 0xff : 0;  
	   int i2 = ip < iEnd ? in[ip++] & 0xff : 0;  
	   int o0 = i0 >>> 2;  
	   int o1 = ((i0 &   3) << 4) | (i1 >>> 4);  
	   int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);  
	   int o3 = i2 & 0x3F;  
	   out[op++] = map1[o0];  
	   out[op++] = map1[o1];  
	   out[op] = op < oDataLen ? map1[o2] : '='; op++;  
	   out[op] = op < oDataLen ? map1[o3] : '='; op++; }  
	return out; }  
	 
	/**  
	* Decodes a string from Base64 format.  
	* No blanks or line breaks are allowed within the Base64 encoded input data.  
	* @param s  A Base64 String to be decoded.  
	* @return   A String containing the decoded data.  
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.  
	*/ 
	public static String decodeString (String s) {  
	return new String(decode(s)); }  
	 
	/**  
	* Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.  
	* CR, LF, Tab and Space characters are ignored in the input data.  
	* This method is compatible with <code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.  
	* @param s  A Base64 String to be decoded.  
	* @return   An array containing the decoded data bytes.  
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.  
	*/ 
	public static byte[] decodeLines (String s) {  
	char[] buf = new char[s.length()+3];  
	int p = 0;  
	for (int ip = 0; ip < s.length(); ip++) {  
	   char c = s.charAt(ip);  
	   if (c != ' ' && c != '\r' && c != '\n' && c != '\t')  
	      buf[p++] = c; }  
	   while ((p % 4) != 0)  
	       buf[p++] = '0';  
	      
	return decode(buf, 0, p); }  
	 
	/**  
	* Decodes a byte array from Base64 format.  
	* No blanks or line breaks are allowed within the Base64 encoded input data.  
	* @param s  A Base64 String to be decoded.  
	* @return   An array containing the decoded data bytes.  
	* @throws   IllegalArgumentException If the input is not valid Base64 encoded data.  
	*/ 
	public static byte[] decode (String s) {  
	return decode(s.toCharArray()); }  
	 
	/**  
	* Decodes a byte array from Base64 format.  
	* No blanks or line breaks are allowed within the Base64 encoded input data.  
	* @param in  A character array containing the Base64 encoded data.  
	* @return    An array containing the decoded data bytes.  
	* @throws    IllegalArgumentException If the input is not valid Base64 encoded data.  
	*/ 
	public static byte[] decode (char[] in) {  
	return decode(in, 0, in.length); }  
	 
	/**  
	* Decodes a byte array from Base64 format.  
	* No blanks or line breaks are allowed within the Base64 encoded input data.  
	* @param in    A character array containing the Base64 encoded data.  
	* @param iOff  Offset of the first character in <code>in</code> to be processed.  
	* @param iLen  Number of characters to process in <code>in</code>, starting at <code>iOff</code>.  
	* @return      An array containing the decoded data bytes.  
	* @throws      IllegalArgumentException If the input is not valid Base64 encoded data.  
	*/ 
	public static byte[] decode (char[] in, int iOff, int iLen) {  
	if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");  
	while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--;  
	int oLen = (iLen*3) / 4;  
	byte[] out = new byte[oLen];  
	int ip = iOff;  
	int iEnd = iOff + iLen;  
	int op = 0;  
	while (ip < iEnd) {  
	   int i0 = in[ip++];  
	   int i1 = in[ip++];  
	   int i2 = ip < iEnd ? in[ip++] : 'A';  
	   int i3 = ip < iEnd ? in[ip++] : 'A';  
	   if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)  
	      throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");  
	   int b0 = map2[i0];  
	   int b1 = map2[i1];  
	   int b2 = map2[i2];  
	   int b3 = map2[i3];  
	   if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)  
	      throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");  
	   int o0 = ( b0       <<2) | (b1>>>4);  
	   int o1 = ((b1 & 0xf)<<4) | (b2>>>2);  
	   int o2 = ((b2 &   3)<<6) |  b3;  
	   out[op++] = (byte)o0;  
	   if (op<oLen) out[op++] = (byte)o1;  
	   if (op<oLen) out[op++] = (byte)o2; }  
	return out; }  
	 
	//Dummy constructor.  
	private Base64Coder() {}  
	 
	} // end class Base64Coder 